The Role of Time and Frequency in the MTSAT Satellite-Based Augmentation System (MSAS)

Abstract

The MTSAT Satellite-based Augmentation System (MSAS) is a satellite-based augmentation system (SBAS) for navigation. The MSAS is one of several applications that shares the use of the Multifunctional Transport Satellite (MTSAT), a geostationary earth orbiting (GEO) satellite, which will be launched by the Japanese Ministry of Transport in August 1999. The MSAS design is based on the development of the US Wide Area Augmentation System (WAAS) and therefore may be familiar to those who are acquainted with the WAAS. Time and frequency play a critical role in four areas within MSAS, and these areas are the focus of this paper. Firstly, MSAS performs several functions. One - it collects data from the NA VSTAR Global Positioning System (GPS); two - it provides an independent ranging signal from MTSAT to supplement the navigation signals from the GPS constellotion; three - it provides differential corrections to improve the navigation capability of the GPS; four - it provides the offset of MSAS Network Time (MNT) from Coordinated Universal Time (UTC); andpve - it provides system integrity information to the user. With these functions, the MSAS can become the primary means of time distribution and synchronization within Japan and other areas under the footprint of the MTSAT. The accuracy and precision attainable by MSAS is critically dependent on the performance of the time and frequency subsystems in the four areas of discussion. The first area of discussion is the manner in which the data recording system tags its observations. Accurate recording of the time of observations is essential in order to measure the timeliness (latency) of all transmitted information. This information is based on algorithm that derive their input from data collected from a network of eight data collection sites,including four Ground Monitoring Stations (GMS) and four Monitor and Ranging Stations (MRS). Each GMS/MRS has three independent, free-running cesium-beam frequency standards.

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Document Details

Document Type
Technical Report
Publication Date
Dec 01, 1998
Accession Number
ADA509502

Entities

People

  • Aileen S. Nii
  • Toru Ishita

Organizations

  • NEC

Tags

DTIC Thesaurus Topics

  • Artificial Satellites
  • Clocks
  • Frequency
  • Frequency Standards
  • Geosynchronous Orbits
  • Geosynchronous Satellites
  • Global Positioning Systems
  • K Band
  • Measurement
  • Navigation
  • Observation
  • Processing Equipment
  • Satellite Orbits
  • Signal Generators
  • Spacecraft
  • Standards
  • Time Intervals

Readers

  • Positioning, Navigation, and Timing (PNT) Technology.
  • Systems Analysis and Design

Technology Areas

  • Space
  • Space - Satellites